Daily Politics and Economics comment. Co-Author of How to Lose a Referendum – the Definitive Story of Why Britain Voted for Brexit [http://bit.ly/2ryynRG]. Economics and Politics teacher in London. 7 years' Independent experience after 4 years in the state sector. Prior to that a management consultant. All opinions here are my own

Two months before the 2011 Scottish Assembly election, opinion polls put the Labour Party 15% ahead of Alex Salmond’s SNP. The SNP won that election by 15%, managing to gain a majority in the Scottish Assembly despite an election system (AMS) expressly designed to stop any party getting a majority. Thus the mandate for an independence referendum for Scotland was granted.

Salmond, who I feel will be remembered as one of the most effective politicians we have ever had in terms of actually achieving what he believes in, reckons that this is why the opinion polls at the moment, which place the Yes campaign on 40% at the most should be looked at with scepticism. Whilst there is a certain amount of ‘Mandy Rice-Davies’ about this (as in “he would say that, wouldn’t he”), I actually think Salmond is right that we could be in for quite a surprise in September.

Salmond has to remain as positive as possible because of what psephologists call the ‘bandwagon effect’, in which voters, some of whom just want to be on the winning side, might switch their allegiances to whichever side had the most positive momentum. Salmond is aware that at the moment, with the Yes side behind in all the polls, he needs to make sure they don’t lose out to the bandwagon effect. But I also wonder whether Salmond knows something that most of us don’t.

That something, I would guess, is that there is a mass of previously ‘hidden’ potential voters, mainly in the poorer areas of the country, or the more isolated, or amongst the young, who have not voted before, are not on the lists of people that pollsters are speaking to, and who could make a difference in this referendum. The Yes campaign have been extremely imaginative in their approach and I would think that as part of that they are pounding the streets, registering voters, persuading people to turnout, and if those people aren’t being counted now, they could absolutely count on September the 18th. I have a gut feeling that these ‘hidden voters’ are more likely to vote ‘Yes’. Which is why I don’t think we should trust the opinion polls right now.